THE COMMON CAROTID ARTERIES 485 



Peculiarities as to Point of Division. The most important peculiarities of this vessel, in 

 a surgical point of view, relate to its place of division in the neck. In the majority of abnormal 

 cases this occurs higher than usual, the artery dividing into two branches opposite the hyoid 

 bone, or even higher ; more rarely it occurs below, opposite the middle of the larynx or the 

 lower border of the cricoid cartilage ; and one case is related by Morgagni where the common 

 carotid, only an inch and a half in length, divided at the root of the neck. Very rarely the 

 common carotid ascends in the neck without any subdivision, the internal carotid being wanting ; 

 and in a few cases the common carotid has been found to be absent, the external and internal 

 carotids arising directly from the arch of the aorta. This peculiarity existed on both sides in 

 some instances, on one side in others. 



Occasional Branches. The common carotid usually gives off no branch previous to its 

 bifurcation ; but it occasionally gives origin to the superior thyroid or its laryngeal branch, the 

 ascending pharyngeal, the inferior thyroid, or, more rarely, the vertebral artery. 



Surface Marking. The carotid arteries are covered throughout their entire extent by the 

 Sterno-mastoid muscle, but their course does not correspond to the anterior border of the muscle, 

 which passes in a somewhat curved direction from the mastoid process to the sterno-clavicular 

 joint. The course of the artery is indicated more exactly by a line drawn from the sternal end 

 of the clavicle below, to a point midway between the angle of the jaw and the mastoid process 

 above. That portion of the line below the level of the upper border of the thyroid cartilage 

 would represent the course of the vessel. 



Surgical Anatomy. The operation of tying the common carotid artery may be necessary 

 in a case of wound of that vessel or its branches, in aneurism, or in a case of pulsating tumor of 

 the orbit or skull. If the wound involves the trunk of the common carotid, it will be necessary 

 to tie the artery above and below the wounded part. But in cases of aneurism, or where one of 

 the branches of the common carotid is wounded in an inaccessible situation, it may be judged 

 necessary to tie the trunk. In such cases the whole of the artery is accessible, and any part may 

 be tied except close to either end. When the case is such as to allow of a choice being made, 

 the lower part of the carotid should never be selected as the spot upon which to place a ligature, 

 for not only is the artery in this situation placed very deeply in the neck, but it is covered 

 by three layers of muscles, and, on the left side, the internal jugular vein, in the great majority 

 of cases, passes obliquely in front of it. Neither should the upper end be selected, for here the 

 superior thyroid vein and its tributaries would give rise to very considerable difficulty in the 

 application of a ligature. The point most favorable for the operation is that part of the vessel 

 which is at the level of the cricoid cartilage. It occasionally happens that the carotid 

 artery bifurcates below its usual position : if the artery be exposed at its point of bifurcation, 

 both divisions of the vessel should be tied near their origin, in preference to tying the trunk 

 of the artery near its termination ; and if, in consequence of the entire absence of the common 

 carotid or from its early division, two arteries, the external and internal carotids, are met with, 

 the ligature should be placed on that vessel which is found on compression to be connected with 

 the disease. 



In this operation the direction of the vessel and the inner margin of the Sterno-mastoid are 

 the chief guides to its performance. The patient should be placed on his back with the head 

 thrown back and turned slightly to the opposite side : an incision is to be made, three inches 

 long, in the direction of the anterior border of the Sterno-mastoid, so that the centre corresponds 

 to the level of the cricoid cartilage : after dividing the integument, superficial fascia, and 

 Platysma, the deep fascia must be cut through on a director, so as to avoid wounding 

 numerous small veins that are usually found beneath. The head may now be brought forward 

 so as to relax the parts somewhat, and the margins of the wound held asunder by retractors. 

 The descendens hypoglossi nerve may now be exposed, and must be avoided, and, the sheath of 

 the vessel having been raised by forceps, is to be opened to a small extent over the artery at its 

 inner side. The internal jugular vein may present itself alternately distended and relaxed ; this 

 should be compressed both above and below, and drawn outward, in order to facilitate the opera- 

 tion. The aneurism needle is passed from the outside, care being taken to keep the needle in 

 close contact with' the artery, and thus avoid the risk of injuring the internal jugular vein or 

 including the vagus nerve. Before the ligature is tied it should be ascertained that nothing but 

 the artery is included in it. 



Ligature of the Common Carotid at the Lower Part of the Neck. This operation is 

 sometimes required in cases of aneurism of the upper part of the carotid, especially if the sac is 

 of large size. It is best performed by dividing the sternal origin of the Sterno-mastoid muscle, 

 but may be done in some cases, if the aneurism is not of very large size, by an incision 

 along the anterior border of the Sterno-mastoid, extending down to the sterno-clavicular articula- 

 tion, and by then retracting the muscle. The easiest and best plan, however, is to make an 

 incision two or three inches long down the lower part of the anterior border of the Sterno- 

 mastoid muscle to the sterno-clavicular joint, and a second incision, starting from the termination 

 of the first, along the upper border of the clavicle for about two inches. This incision is made 

 through the superficial and deep fascia, and the sternal origin of the muscle exposed. This is to 

 be divided on 3, director, and turned up, with the superficial structures, as a triangular flap. 

 Some loose connective tissue is to be divided or torn through, and the outer border of the 

 Sterno-hyoid muscle exposed. In doing this care must be taken not to wound the anterior 

 jugular vein, which crosses the muscle to reach the external jugular or subclavian vein. The 

 Sterno-hyoid, and with it the Sterno-thyroid. are to be drawn inward by means of a retractor^ 



